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TENNESSEE — Steve Hobbs, structural engineer for the U.S. Army Corps of Engineers St. Louis District and Level I certified for rope access technician, prepares to inspect the top chords of the railroad truss at the Holston Army Ammunition Plant in Tennessee. The St. Louis District employs this unique technique to conduct inspections of bridges, dams and other structures in the Corps of Engineers and other federal agencies. (Photo by George Stringham)

ILLLINOIS — Tom Ruf (right), structural engineer with the U.S. Army Corps of Engineers St. Louis District, inspects one of the four tainter gates on Carlyle Dam, Ill., in August 2011. To the left is Ropeworks technician Blake Dieste. (Photo by George Stringham)

ST. LOUIS, Mo. — As the infrastructure in the U.S. gets older, structural materials deteriorate due to weather, loads and damage through usage. The ability to perform critical and detailed inspections of them becomes a high priority and the U.S. Army Corps of Engineers St. Louis District has a structural inspection team that does this in an unusual manner -- ropes.

The St. Louis District has a large group of structural engineers in the Corps of Engineers who are trained in rope access techniques to inspect hydraulic steel structures and bridges. Typical hydraulic steel structures in the St. Louis District are tainter, miter and lift gates, culvert valves and bulkheads.

In the past, it was difficult, if not impossible, for structural engineers to inspect various portions of large steel or concrete structures because they were not able to physically get to the areas of the project requiring inspection. To get a floating plant or a crane to move inspectors to the required inspection positions on the structure was prohibitive due to the cost.

Eight years ago, two of the District's structural engineers, Tom Ruf and Rob Kelsey, both avid mountain climbers and accomplished structural steel designers, suggested that rope access techniques could be safely employed to provide access to inspect our large steel structures.

Since then, six more structural engineers from the District have achieved their certification, bringing the total to eight personnel that are qualified to perform rope access inspections. Corps-wide there are only a few Districts that have engineers certified to conduct these types of inspections.

The structural inspection team performs rope access, rather than using more traditional methods like scaffolding, cradles or equipment like scissor lifts or cherry pickers for three primary reasons: it is safe, versatile and economical.

First and foremost, it's safe. A two-rope system is used where one rope serves as the working line and supports the worker and the other is a safety line provides complete independent redundancy.

This means of inspection is also versatile, allowing the inspector the freedom and mobility to move around more easily than other methods.

"Our regulations require us to get up-close and personal with our structures," explained Steve Hobbs, structural engineer with the St. Louis District. "This access technique allows us to get close enough where we can look at critical areas closely, take pictures and perform other inspection tasks we wouldn't otherwise be able to do."

The rope system is also installed and dismantled quickly, allowing the inspection teams to move from one portion of the job to the next more quickly than other methods. This translates into it being more efficient, resulting in a more economical means to perform the work. Not using the other methods also minimizes many of the mobilization and setup costs associated with them as well.

The team has not just used their expertise to benefit the St. Louis District, though. They've also performed inspections for a four-span railroad bridge at the Holston Army Ammunition Plant in Tennessee, tainter gates at dams in the Kansas City District, and, most recently, tainter gates at dams on the Missouri River for the Omaha District.

After the record setting floods on the Missouri River in 2011, the Northwestern Division and Omaha District were eager to have the six main stem dams on the river inspected as soon as allowable, given the elevated pool levels the dams withstood.

The St. Louis District's rope access team was called on perform this task, which primarily encompassed 95 gate structures at the six dams on the Missouri River. The timeline needed to complete the work was tight, so they reached out to certified members of the Philadelphia and New England Districts.

St. Louis and Philadelphia Districts inspected Garrison and Fort Randall dams together. This was to establish continuity between the two teams, making sure they were addressing the same issues and noting discrepancies or concerns in a similar manner.

The teams split up the remaining work with St. Louis taking Big Bend and Oahe dams and Philadelphia taking Gavins Point and Fort Peck dam. A certified inspector from New England District also assisted at Fort Peck. To the relief of the Northwestern Division and Omaha District, no major deficiencies were discovered.

"For us, the quick response and collection of this data was critical," stated John LaRandeau, Navigation Support Manager for the Northwestern Division. "This was a record event and we needed to find out as soon as possible how they performed and whether or not they would be in a position to perform during the next flood season."

The District's the team has expanded in several significant areas -- the types of structures being inspected, the composition of the team, the variety of the customers being serviced and the use of partnering concepts with other rope access trained districts. Their willingness to find ways to share the knowledge of this type of inspection, coupled with the willingness and planning to inspect new and larger types of structures, reflects the regional and national stature of this effort.